x86/hvm: Drop hvm_{get,set}_guest_bndcfgs() and use {get,set}_regs() instead

hvm_{get,set}_guest_bndcfgs() are thin wrappers around accessing MSR_BNDCFGS.

MPX was implemented on Skylake uarch CPUs and dropped in subsequent CPUs, and
is disabled by default in Xen VMs.

It would be nice to move all the logic into vmx_msr_{read,write}_intercept(),
but the common HVM migration code uses guest_{rd,wr}msr().  Therefore, use
{get,set}_regs() to reduce the quantity of "common" HVM code.

In lieu of having hvm_set_guest_bndcfgs() split out, use some #ifdef
CONFIG_HVM in guest_wrmsr().  In vmx_{get,set}_regs(), split the switch
statements into two depending on whether the require remote VMCS acquisition
or not.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index b530e986e86cea8232cf631794cb1934dafc176f..d7d3299b431eeb6416786ce2c903a90040b57bee 100644 (file)
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -324,43 +324,6 @@ int hvm_set_guest_pat(struct vcpu *v, uint64_t guest_pat)
     return 1;
 }
 
-bool hvm_set_guest_bndcfgs(struct vcpu *v, u64 val)
-{
-    if ( !hvm_funcs.set_guest_bndcfgs ||
-         !is_canonical_address(val) ||
-         (val & IA32_BNDCFGS_RESERVED) )
-        return false;
-
-    /*
-     * While MPX instructions are supposed to be gated on XCR0.BND*, let's
-     * nevertheless force the relevant XCR0 bits on when the feature is being
-     * enabled in BNDCFGS.
-     */
-    if ( (val & IA32_BNDCFGS_ENABLE) &&
-         !(v->arch.xcr0_accum & (X86_XCR0_BNDREGS | X86_XCR0_BNDCSR)) )
-    {
-        uint64_t xcr0 = get_xcr0();
-        int rc;
-
-        if ( v != current )
-            return false;
-
-        rc = handle_xsetbv(XCR_XFEATURE_ENABLED_MASK,
-                           xcr0 | X86_XCR0_BNDREGS | X86_XCR0_BNDCSR);
-
-        if ( rc )
-        {
-            HVM_DBG_LOG(DBG_LEVEL_1, "Failed to force XCR0.BND*: %d", rc);
-            return false;
-        }
-
-        if ( handle_xsetbv(XCR_XFEATURE_ENABLED_MASK, xcr0) )
-            /* nothing, best effort only */;
-    }
-
-    return alternative_call(hvm_funcs.set_guest_bndcfgs, v, val);
-}
-
 /*
  * Get the ratio to scale host TSC frequency to gtsc_khz. zero will be
  * returned if TSC scaling is unavailable or ratio cannot be handled

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index bcd0ec572c6f07cea7d7543659e0f0fc8acafbdf..c44cf8f5d4254cc1a5aeb792e66aa91564949279 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1212,28 +1212,6 @@ static int vmx_get_guest_pat(struct vcpu *v, u64 *gpat)
     return 1;
 }
 
-static bool vmx_set_guest_bndcfgs(struct vcpu *v, u64 val)
-{
-    ASSERT(cpu_has_mpx && cpu_has_vmx_mpx);
-
-    vmx_vmcs_enter(v);
-    __vmwrite(GUEST_BNDCFGS, val);
-    vmx_vmcs_exit(v);
-
-    return true;
-}
-
-static bool vmx_get_guest_bndcfgs(struct vcpu *v, u64 *val)
-{
-    ASSERT(cpu_has_mpx && cpu_has_vmx_mpx);
-
-    vmx_vmcs_enter(v);
-    __vmread(GUEST_BNDCFGS, val);
-    vmx_vmcs_exit(v);
-
-    return true;
-}
-
 static void vmx_handle_cd(struct vcpu *v, unsigned long value)
 {
     if ( !paging_mode_hap(v->domain) )
@@ -2427,6 +2405,7 @@ static uint64_t vmx_get_reg(struct vcpu *v, unsigned int reg)
     uint64_t val = 0;
     int rc;
 
+    /* Logic which doesn't require remote VMCS acquisition. */
     switch ( reg )
     {
     case MSR_SPEC_CTRL:
@@ -2438,13 +2417,25 @@ static uint64_t vmx_get_reg(struct vcpu *v, unsigned int reg)
             domain_crash(d);
         }
         return val;
+    }
+
+    /* Logic which maybe requires remote VMCS acquisition. */
+    vmx_vmcs_enter(v);
+    switch ( reg )
+    {
+    case MSR_IA32_BNDCFGS:
+        __vmread(GUEST_BNDCFGS, &val);
+        break;
 
     default:
         printk(XENLOG_G_ERR "%s(%pv, 0x%08x) Bad register\n",
                __func__, v, reg);
         domain_crash(d);
-        return 0;
+        break;
     }
+    vmx_vmcs_exit(v);
+
+    return val;
 }
 
 static void vmx_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
@@ -2452,6 +2443,7 @@ static void vmx_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
     struct domain *d = v->domain;
     int rc;
 
+    /* Logic which doesn't require remote VMCS acquisition. */
     switch ( reg )
     {
     case MSR_SPEC_CTRL:
@@ -2462,6 +2454,15 @@ static void vmx_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
                    __func__, v, reg, rc);
             domain_crash(d);
         }
+        return;
+    }
+
+    /* Logic which maybe requires remote VMCS acquisition. */
+    vmx_vmcs_enter(v);
+    switch ( reg )
+    {
+    case MSR_IA32_BNDCFGS:
+        __vmwrite(GUEST_BNDCFGS, val);
         break;
 
     default:
@@ -2469,6 +2470,7 @@ static void vmx_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
                __func__, v, reg, val);
         domain_crash(d);
     }
+    vmx_vmcs_exit(v);
 }
 
 static struct hvm_function_table __initdata vmx_function_table = {
@@ -2792,12 +2794,6 @@ const struct hvm_function_table * __init start_vmx(void)
         vmx_function_table.tsc_scaling.setup = vmx_setup_tsc_scaling;
     }
 
-    if ( cpu_has_mpx && cpu_has_vmx_mpx )
-    {
-        vmx_function_table.set_guest_bndcfgs = vmx_set_guest_bndcfgs;
-        vmx_function_table.get_guest_bndcfgs = vmx_get_guest_bndcfgs;
-    }
-
     lbr_tsx_fixup_check();
     ler_to_fixup_check();
 

diff --git a/xen/arch/x86/include/asm/hvm/hvm.h b/xen/arch/x86/include/asm/hvm/hvm.h
index 3ab177d9dd514843c041838b4ed089b8cf93e828..842f98763c4bd4d454e6d7d7ccaff72fcf7ccbda 100644 (file)
--- a/xen/arch/x86/include/asm/hvm/hvm.h
+++ b/xen/arch/x86/include/asm/hvm/hvm.h
@@ -149,9 +149,6 @@ struct hvm_function_table {
     int  (*get_guest_pat)(struct vcpu *v, u64 *);
     int  (*set_guest_pat)(struct vcpu *v, u64);
 
-    bool (*get_guest_bndcfgs)(struct vcpu *v, u64 *);
-    bool (*set_guest_bndcfgs)(struct vcpu *v, u64);
-
     void (*set_tsc_offset)(struct vcpu *v, u64 offset, u64 at_tsc);
 
     void (*inject_event)(const struct x86_event *event);
@@ -291,8 +288,6 @@ void hvm_set_segment_register(struct vcpu *v, enum x86_segment seg,
 
 void hvm_set_info_guest(struct vcpu *v);
 
-bool hvm_set_guest_bndcfgs(struct vcpu *v, u64 val);
-
 int hvm_vmexit_cpuid(struct cpu_user_regs *regs, unsigned int inst_len);
 void hvm_migrate_timers(struct vcpu *v);
 void hvm_do_resume(struct vcpu *v);
@@ -479,12 +474,6 @@ static inline unsigned long hvm_get_shadow_gs_base(struct vcpu *v)
     return alternative_call(hvm_funcs.get_shadow_gs_base, v);
 }
 
-static inline bool hvm_get_guest_bndcfgs(struct vcpu *v, u64 *val)
-{
-    return hvm_funcs.get_guest_bndcfgs &&
-           alternative_call(hvm_funcs.get_guest_bndcfgs, v, val);
-}
-
 #define has_hvm_params(d) \
     ((d)->arch.hvm.params != NULL)
 
@@ -767,7 +756,6 @@ int hvm_guest_x86_mode(struct vcpu *v);
 unsigned long hvm_get_shadow_gs_base(struct vcpu *v);
 void hvm_cpuid_policy_changed(struct vcpu *v);
 void hvm_set_tsc_offset(struct vcpu *v, uint64_t offset, uint64_t at_tsc);
-bool hvm_get_guest_bndcfgs(struct vcpu *v, uint64_t *val);
 
 /* End of prototype list */
 

diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index 71cbfa8ee37de6d262102d1875342fd0d9150196..2cc355575d4571bc1dc2944b1aa10b06a2e5c762 100644 (file)
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -30,6 +30,7 @@
 #include <asm/msr.h>
 #include <asm/pv/domain.h>
 #include <asm/setup.h>
+#include <asm/xstate.h>
 
 #include <public/hvm/params.h>
 
@@ -323,10 +324,9 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
         break;
 
     case MSR_IA32_BNDCFGS:
-        if ( !cp->feat.mpx || !is_hvm_domain(d) ||
-             !hvm_get_guest_bndcfgs(v, val) )
+        if ( !cp->feat.mpx ) /* Implies Intel HVM only */
             goto gp_fault;
-        break;
+        goto get_reg;
 
     case MSR_IA32_XSS:
         if ( !cp->xstate.xsaves )
@@ -593,11 +593,33 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
         ret = guest_wrmsr_x2apic(v, msr, val);
         break;
 
+#ifdef CONFIG_HVM
     case MSR_IA32_BNDCFGS:
-        if ( !cp->feat.mpx || !is_hvm_domain(d) ||
-             !hvm_set_guest_bndcfgs(v, val) )
+        if ( !cp->feat.mpx || /* Implies Intel HVM only */
+             !is_canonical_address(val) || (val & IA32_BNDCFGS_RESERVED) )
             goto gp_fault;
-        break;
+
+        /*
+         * While MPX instructions are supposed to be gated on XCR0.BND*, let's
+         * nevertheless force the relevant XCR0 bits on when the feature is
+         * being enabled in BNDCFGS.
+         */
+        if ( (val & IA32_BNDCFGS_ENABLE) &&
+             !(v->arch.xcr0_accum & (X86_XCR0_BNDREGS | X86_XCR0_BNDCSR)) )
+        {
+            uint64_t xcr0 = get_xcr0();
+
+            if ( v != current ||
+                 handle_xsetbv(XCR_XFEATURE_ENABLED_MASK,
+                               xcr0 | X86_XCR0_BNDREGS | X86_XCR0_BNDCSR) )
+                goto gp_fault;
+
+            if ( handle_xsetbv(XCR_XFEATURE_ENABLED_MASK, xcr0) )
+                /* nothing, best effort only */;
+        }
+
+        goto set_reg;
+#endif /* CONFIG_HVM */
 
     case MSR_IA32_XSS:
         if ( !cp->xstate.xsaves )